I'm a little late in linking this story but with the excitement about the new iPads, I thought it still relevant. Harry is a top-flight tech writer who went public about the fact that his iPad is his primary computer about a year ago. Harry even guested on the Mac Power Users (Episode 71) explaining how he pulled it off.
After a year, Harry writes he still loves his iPad but is not so much a revolutionary as he first was since others are also using the iPad as their primary computer. For example, see M.G. Siegler.
I love my iPad and use the heck out of it but I'd put my Mac/iPad ratio closer to 60/40. I still use a Mac more often but anything away from my desk is done on an iPad (and I'm finding increasingly creative excuses to get away from my desk).